| Year | Value | | 2022 | 37.797862994102 | | 2021 | 37.773962369295 | | 2020 | 36.382083485926 | | 2019 | 36.588960762212 | | 2018 | 37.067555974517 | | 2017 | 37.489058274117 | | 2016 | 36.869794985508 | | 2015 | 37.327302834969 | | 2014 | 38.000938099073 | | 2013 | 37.765099191815 | | 2012 | 38.457983636659 | | 2011 | 39.088399176803 | | 2010 | 40.229164606011 | | 2009 | 39.212487654118 | | 2008 | 40.656249170005 | | 2007 | 40.286945545221 | | 2006 | 39.10777447531 | | 2005 | 37.672827787723 | | 2004 | 37.389169066773 | | 2003 | 35.388654430054 | | 2002 | 33.52581406992 | | 2001 | 33.124192513353 | | 2000 | 32.934101254157 | | 1999 | 32.969917161507 | | 1998 | 34.805678120297 | | 1997 | 35.814779162978 | | 1996 | 35.224203932382 | | 1995 | 36.609751273544 | | 1994 | 38.313404285447 | | 1993 | 37.99054047127 | | 1992 | 36.71147458347 | | 1991 | 35.462285573373 | | 1990 | 34.569437939552 | | 1989 | 34.288697702738 |
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